Michael R. Resetarits Forum Moderator 22 Posts
Re: Is there a good way to calculate the height of stage in a distillation column?6 May 2010 at 1:29pm
I have attached two PDFs (links below) that discuss the effect of Marangoni Negative systems. It is generally agreed that HETP is at least two times greater for Marangoni negative systems but I am not sure that that is the whole story as you will see from the Koshy- Rukovena paper and the effect that changes in lambda has on the HETP. A high lambda system with a Marangoni negative affect is going to have an HETP increased at least in the range indicated by Kister. I am sorry but I don’t know how to predict the HETP closer than that. Note from Figure 3 of the Koshy-Rukovena paper that a system with a high or low lambda can have its HETP increase be even greater than three times.
I'm working on a distillation column for a six-part multi-component distillation column. It contains structured packing. I estimated about eight stages with a model and came up with approximately the same answer with pseudo-McCabe-Thiele. I was careful to pick the correct heavy key and light key. Then, I realized I did not have a good way to calculate the height of stage. The model, like most, only tells you the number of stages not the height of stage or Z, the final height of theoretical packing. Kister would say 1-3 feet as an assumption (based on gas resistance), or I could estimate it using a KG or KL. Empirical data would help. I assume that the oil, a collection of C10+, would pose the greatest resistance, which makes calculating an H stage even more difficult. The feed is trace water, toluene and oils. Any advice or reference that might be useful in solving this dilemma?
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